import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution16 {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return bool布尔型
     */
    public boolean isSymmetrical (TreeNode pRoot) {
        // write code here
        if(pRoot == null) {
            return true;
        }
        return istrue(pRoot.left,pRoot.right);
    }
    private boolean istrue(TreeNode left,TreeNode right) {
        if(left == null && right == null) {
            return true;
        } else if(left == null) {
            return false;
        } else if(right == null) {
            return false;
        } else {
            if(left.val != right.val) {
                return false;
            }
        }
        return istrue(left.left,right.right) && istrue(left.right,right.left);

    }
}